An X-Y motion platform system is a fundamental part of many digital control processing apparatuses and electronic processing apparatuses such as a worktable for laser processing apparatus, a surface attaching apparatus and a two-dimension (2D) measuring apparatus. A motion control system of the existing X-Y motion platform is mainly constituted by a computer, a motion controller, a step motor and related software. A conventional X-Y motion platform includes two (motor-driven) linear motion units, each of which generally includes a screw rod and a guide rail, and the combined motion of these two linear motion units generates a planar motion with two degrees of freedom (i.e. directions of X and Y axes) of the worktable.
However, an error tends to occur during the control on the motion of the worktable. For example, in the case that the worktable is desired to move to an ideal position with coordinates (302 mm, 216 mm), if the worktable is actually moved to a position with coordinates (301.98 mm, 216.07 mm), an error of (0.02 mm, 0.03 mm), which is also called as absolute movement error, is caused. The reason for causing the absolute movement error of the existing X-Y motion platform includes:
1) electric motor factors, i.e. an error caused by the electric motor per se, and an accumulative error is caused if the step motor stalls;
2) screw rod factors, i.e. an error in the motion screw rod per se, which depends on the category of the screw rod, for example, as shown in FIG. 1 showing lead errors (in a unit of μm) at various travels of the screw rod, an error of 6 μm is caused for a travel of 500 mm of the screw rod in the category CO with the highest system accuracy;
3) return-to-zero error, that is, an error might occur each time the motion platform returns to the origin, and hence the motion of the motion platform cannot always start at the same position each time;
4) assembly error, that is, an unavoidable error occurs to the assembly of the X-Y motion platform; and
5) other errors such as temperature and humidity errors.
As such, the system accuracy of the existing conventional X-Y motion platform is 10 μm to 50 μm.
In order to improve the system accuracy of an X-Y motion platform, an X-Y motion platform based on linear motor and a grating ruler X-Y motion platform based on marble platform have been proposed. The X-Y motion platform based on linear motor employs a better linear motor and a high-accuracy screw rod, and has system accuracy of ±10 μm considering by all the error factors. Likewise, the grating ruler X-Y motion platform based on marble platform employs a better linear motor and a high-accuracy screw rod, and has some essential parts made of marble which is of the grade shown in FIG. 2, however, due to the jitter interference of the grating ruler, the accumulative error cannot be eliminated in the background of large noise, the design requirements for hardware are strict, and the overall system accuracy is ±5 μm.
To improve the system accuracy of the X-Y motion platform in the prior art, stricter requirements are laid on the assembly and selection of devices, the system accuracy is limited, and further improvements are required.